Add real-time consumer panel and paginated transaction results

- Implement WebSocket endpoint (/ws/fraud-results) in API for real-time fraud detection updates
- Add Redis pub/sub listener in API to broadcast consumer results to connected WebSocket clients
- Update consumer to publish fraud detection results to Redis 'fraud_results' channel with transaction details
- Add WebSocket connection logic in frontend with auto-reconnect (exponential backoff)
- Display real-time consumer status panel with fraud score color coding and decision status
- Implement client-side transaction results pagination (10/25/50 items per page)
- Add pagination controls: Previous/Next buttons, page indicator, page size selector
- Newest-first transaction sorting (DESC by timestamp)
- Add comprehensive styling for consumer panel and pagination controls
- All frontend components tested and builds successfully

Co-authored-by: Copilot <[email protected]>

api/main.py

@@ -13,7 +13,7 @@ hands off responsibility to the message queue. This separation of concerns is
 fundamental to scalable microservices architecture.
 """
 
-from fastapi import FastAPI, Depends, HTTPException, status
+from fastapi import FastAPI, Depends, HTTPException, status, WebSocket, WebSocketDisconnect
 from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
 from fastapi.middleware.cors import CORSMiddleware
 from pydantic import BaseModel
@@ -23,6 +23,8 @@ import json
 import uuid
 import time
 import logging
+import redis
+import threading
 
 # ══════════════════════════════════════════════════════════════════════════════
 # CONFIGURATION
@@ -85,6 +87,66 @@ def get_kafka_producer():
             raise
     return kafka_producer
 
+# ══════════════════════════════════════════════════════════════════════════════
+# REDIS & WEBSOCKET PUBSUB
+# ══════════════════════════════════════════════════════════════════════════════
+
+redis_client = None
+connected_clients = set()
+pubsub_thread = None
+
+def get_redis_client():
+    """Get or create Redis client"""
+    global redis_client
+    if redis_client is None:
+        try:
+            redis_client = redis.Redis(
+                host="redis",
+                port=6379,
+                decode_responses=True
+            )
+            redis_client.ping()
+            logger.info("[REDIS] Connected to Redis")
+        except Exception as e:
+            logger.warning(f"[REDIS] Connection failed: {e}")
+            redis_client = None
+            raise
+    return redis_client
+
+def start_pubsub_listener():
+    """Start background thread to listen for fraud results on Redis pub/sub"""
+    global pubsub_thread
+    
+    def listen_and_broadcast():
+        try:
+            redis_conn = get_redis_client()
+            pubsub = redis_conn.pubsub()
+            pubsub.subscribe("fraud_results")
+            logger.info("[PUBSUB] Listening to 'fraud_results' channel")
+            
+            for message in pubsub.listen():
+                if message["type"] == "message":
+                    try:
+                        data = json.loads(message["data"])
+                        # Broadcast to all connected WebSocket clients
+                        for client in list(connected_clients):
+                            try:
+                                if not client.client_state.value == 0:  # Check if still connected
+                                    client.send_json(data)
+                            except Exception as e:
+                                logger.warning(f"[PUBSUB] Failed to send to client: {e}")
+                                try:
+                                    connected_clients.discard(client)
+                                except:
+                                    pass
+                    except Exception as e:
+                        logger.error(f"[PUBSUB] Failed to parse message: {e}")
+        except Exception as e:
+            logger.error(f"[PUBSUB] Listener error: {e}")
+    
+    pubsub_thread = threading.Thread(target=listen_and_broadcast, daemon=True)
+    pubsub_thread.start()
+
 # ══════════════════════════════════════════════════════════════════════════════
 # AUTHENTICATION
 # ══════════════════════════════════════════════════════════════════════════════
@@ -211,6 +273,34 @@ async def get_demo_token(user_id: str):
     logger.info(f"[JWT GENERATION] Generated token for user={user_id}")
     return {"access_token": token, "token_type": "bearer"}
 
+@app.websocket("/ws/fraud-results")
+async def websocket_fraud_results(websocket: WebSocket):
+    """
+    WebSocket endpoint for real-time fraud detection results.
+    
+    Clients connect and receive live updates when fraud detection completes.
+    Results are streamed from Redis pub/sub channel via background listener.
+    """
+    await websocket.accept()
+    connected_clients.add(websocket)
+    logger.info(f"[WEBSOCKET] Client connected. Total clients: {len(connected_clients)}")
+    
+    try:
+        # Keep connection alive while client is connected
+        while True:
+            # Wait for any client message (optional heartbeat/ping)
+            data = await websocket.receive_text()
+            logger.debug(f"[WEBSOCKET] Received from client: {data}")
+    except WebSocketDisconnect:
+        connected_clients.discard(websocket)
+        logger.info(f"[WEBSOCKET] Client disconnected. Total clients: {len(connected_clients)}")
+    except Exception as e:
+        logger.error(f"[WEBSOCKET] Error: {e}")
+        try:
+            connected_clients.discard(websocket)
+        except:
+            pass
+
 # ══════════════════════════════════════════════════════════════════════════════
 # STARTUP / SHUTDOWN
 # ══════════════════════════════════════════════════════════════════════════════
@@ -224,6 +314,13 @@ async def startup_event():
     logger.info(f"Topic: {KAFKA_TOPIC}")
     logger.info("Listening for authenticated transaction requests...")
     logger.info("="*80)
+    
+    # Start Redis pub/sub listener for WebSocket broadcasts
+    try:
+        get_redis_client()
+        start_pubsub_listener()
+    except Exception as e:
+        logger.warning(f"[STARTUP] Redis pub/sub not available: {e}")
 
 @app.on_event("shutdown")
 async def shutdown_event():

consumer/decision.py

@@ -122,8 +122,12 @@ class DecisionEngine:
         return decision
     
     def store_result(self, transaction_id: str, decision: str, 
-                     layer1_score: float, layer2_score: float = None) -> None:
-        """Store decision result in Redis for retrieval"""
+                     layer1_score: float, layer2_score: float = None,
+                     transaction_data: dict = None) -> None:
+        """Store decision result in Redis and publish to pub/sub channel"""
+        import json
+        from datetime import datetime
+        
         key = f"result:{transaction_id}"
         value = {
             "decision": decision,
@@ -136,3 +140,25 @@ class DecisionEngine:
         self.redis_client.setex(key, 3600, str(value))
         
         logger.info(f"[RESULT STORAGE] Stored decision in Redis: {key} = {decision}")
+        
+        # Publish to pub/sub channel for real-time WebSocket updates
+        try:
+            # Build message with transaction details for frontend
+            message = {
+                "transaction_id": transaction_id,
+                "decision": decision,
+                "fraud_score": round(layer2_score, 4) if layer2_score is not None else round(layer1_score, 4),
+                "layer1_score": round(layer1_score, 4),
+                "timestamp": datetime.utcnow().isoformat() + "Z"
+            }
+            
+            # Add transaction data if provided (amount, merchant)
+            if transaction_data:
+                message["amount"] = transaction_data.get("amount")
+                message["merchant"] = transaction_data.get("merchant")
+            
+            # Publish to Redis pub/sub channel
+            self.redis_client.publish("fraud_results", json.dumps(message))
+            logger.info(f"[RESULT STORAGE] Published result to pub/sub channel: {transaction_id[:8]}... → {decision}")
+        except Exception as e:
+            logger.error(f"[RESULT STORAGE] Failed to publish to pub/sub: {str(e)}")

consumer/pipeline.py

@@ -193,7 +193,8 @@ def process_transaction(transaction, components):
         transaction_id=transaction_id,
         decision=decision,
         layer1_score=layer1_score,
-        layer2_score=layer2_score
+        layer2_score=layer2_score,
+        transaction_data=transaction  # Pass full transaction for pub/sub message
     )
     
     # ─────────────────────────────────────────────────────────────────────────

frontend/src/App.css

@@ -345,3 +345,170 @@
     font-size: 0.8rem;
   }
 }
+
+/* Consumer Status Card */
+.consumer-card {
+  border-top: 4px solid var(--primary);
+  background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
+}
+
+.consumer-content {
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+}
+
+.connection-status {
+  display: flex;
+  justify-content: center;
+}
+
+.connection-status .status-badge {
+  font-size: 0.875rem;
+  padding: 0.5rem 1rem;
+}
+
+.connection-status .status-badge.connected {
+  background: var(--success);
+  color: white;
+}
+
+.connection-status .status-badge.disconnected {
+  background: var(--error);
+  color: white;
+}
+
+.empty-state {
+  text-align: center;
+  padding: 2rem 1rem;
+  color: var(--text-light);
+}
+
+.empty-state p {
+  margin: 0.5rem 0;
+}
+
+.consumer-status-details {
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
+  background: white;
+  padding: 1rem;
+  border-radius: 0.375rem;
+}
+
+.status-row {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 0.5rem 0;
+  border-bottom: 1px solid var(--border);
+}
+
+.status-row:last-child {
+  border-bottom: none;
+}
+
+.status-row label {
+  font-weight: 600;
+  color: var(--text);
+  font-size: 0.875rem;
+  min-width: 120px;
+}
+
+.status-row span {
+  color: var(--text-light);
+  font-size: 0.875rem;
+  text-align: right;
+  flex: 1;
+  margin-left: 1rem;
+}
+
+/* Pagination Controls */
+.pagination-controls {
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+  padding: 1rem;
+  background: var(--bg);
+  border-radius: 0.375rem;
+  margin-bottom: 1rem;
+}
+
+.pagination-info {
+  text-align: center;
+  font-size: 0.875rem;
+  color: var(--text-light);
+  font-weight: 500;
+}
+
+.pagination-buttons {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 1rem;
+}
+
+.btn-pagination {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  background: var(--primary);
+  color: white;
+  padding: 0.5rem 1rem;
+  border: none;
+  border-radius: 0.375rem;
+  font-size: 0.875rem;
+  font-weight: 500;
+  cursor: pointer;
+  transition: all 0.2s ease;
+  min-width: 100px;
+  justify-content: center;
+}
+
+.btn-pagination:hover:not(:disabled) {
+  background: var(--primary-dark);
+  transform: translateY(-2px);
+  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
+}
+
+.btn-pagination:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.page-indicator {
+  font-size: 0.875rem;
+  font-weight: 600;
+  color: var(--text);
+  min-width: 120px;
+  text-align: center;
+}
+
+.page-size-selector {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 0.75rem;
+}
+
+.page-size-selector label {
+  font-size: 0.875rem;
+  font-weight: 500;
+  color: var(--text);
+}
+
+.select-input {
+  padding: 0.5rem;
+  border: 1px solid var(--border);
+  border-radius: 0.375rem;
+  font-size: 0.875rem;
+  cursor: pointer;
+  background: white;
+}
+
+.select-input:focus {
+  outline: none;
+  border-color: var(--primary);
+  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
+}

frontend/src/App.tsx

@@ -1,5 +1,5 @@
-import React, { useState } from 'react';
-import { AlertCircle, CheckCircle, Clock, Lock, Send } from 'lucide-react';
+import React, { useState, useEffect, useRef } from 'react';
+import { AlertCircle, CheckCircle, Clock, Lock, Send, Wifi, WifiOff, ChevronLeft, ChevronRight } from 'lucide-react';
 import axios from 'axios';
 import './App.css';
 
@@ -28,6 +28,15 @@ interface Result {
   timestamp: string;
 }
 
+interface FraudResult {
+  transaction_id: string;
+  decision: string;
+  fraud_score: number;
+  amount?: number;
+  merchant?: string;
+  timestamp: string;
+}
+
 // Use localhost when browser accesses from host machine
 const API_BASE_URL = 'http://localhost:8000';
 
@@ -46,9 +55,72 @@ const App: React.FC = () => {
   });
 
   const [results, setResults] = useState<Result[]>([]);
+  const [consumerStatus, setConsumerStatus] = useState<FraudResult | null>(null);
+  const [wsConnected, setWsConnected] = useState(false);
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const [success, setSuccess] = useState<string | null>(null);
+  
+  // Pagination state
+  const [currentPage, setCurrentPage] = useState(1);
+  const [pageSize, setPageSize] = useState(25);
+  
+  const wsRef = useRef<WebSocket | null>(null);
+  const reconnectTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+  // WebSocket connection management
+  useEffect(() => {
+    const connectWebSocket = () => {
+      try {
+        const wsUrl = 'ws://localhost:8000/ws/fraud-results';
+        const ws = new WebSocket(wsUrl);
+        
+        ws.onopen = () => {
+          console.log('[WEBSOCKET] Connected to fraud results stream');
+          setWsConnected(true);
+        };
+        
+        ws.onmessage = (event) => {
+          try {
+            const data = JSON.parse(event.data) as FraudResult;
+            console.log('[WEBSOCKET] Received fraud result:', data);
+            setConsumerStatus(data);
+          } catch (e) {
+            console.error('[WEBSOCKET] Failed to parse message:', e);
+          }
+        };
+        
+        ws.onerror = (error) => {
+          console.error('[WEBSOCKET] Error:', error);
+          setWsConnected(false);
+        };
+        
+        ws.onclose = () => {
+          console.log('[WEBSOCKET] Disconnected, attempting reconnect...');
+          setWsConnected(false);
+          // Exponential backoff reconnection: 1s → 2s → 4s → 8s
+          const delay = Math.min(1000 * Math.pow(2, 3), 8000);
+          reconnectTimeoutRef.current = setTimeout(connectWebSocket, delay);
+        };
+        
+        wsRef.current = ws;
+      } catch (e) {
+        console.error('[WEBSOCKET] Connection failed:', e);
+        setWsConnected(false);
+      }
+    };
+    
+    connectWebSocket();
+    
+    return () => {
+      if (wsRef.current) {
+        wsRef.current.close();
+      }
+      if (reconnectTimeoutRef.current) {
+        clearTimeout(reconnectTimeoutRef.current);
+      }
+    };
+  }, []);
 
   // Generate JWT token
   const generateToken = async () => {
@@ -173,6 +245,19 @@ const App: React.FC = () => {
     });
   };
 
+  // Pagination helpers
+  const totalPages = Math.ceil(results.length / pageSize);
+  const paginatedResults = results.slice(
+    (currentPage - 1) * pageSize,
+    currentPage * pageSize
+  );
+
+  const getFraudScoreColor = (score: number): string => {
+    if (score < 0.3) return '#10b981'; // Green - low risk
+    if (score < 0.7) return '#f59e0b'; // Yellow - medium risk
+    return '#ef4444'; // Red - high risk
+  };
+
   return (
     <div className="app">
       <div className="header">
@@ -181,6 +266,88 @@ const App: React.FC = () => {
       </div>
 
       <div className="container">
+        {/* Consumer Status Panel */}
+        <section className="card consumer-card">
+          <div className="card-header">
+            <div style={{ display: 'flex', alignItems: 'center', gap: '8px' }}>
+              {wsConnected ? (
+                <Wifi size={20} style={{ color: '#10b981' }} />
+              ) : (
+                <WifiOff size={20} style={{ color: '#ef4444' }} />
+              )}
+              <h2>Real-Time Consumer Pipeline</h2>
+            </div>
+          </div>
+          <div className="consumer-content">
+            <div className="connection-status">
+              <span className={`status-badge ${wsConnected ? 'connected' : 'disconnected'}`}>
+                {wsConnected ? '● Connected' : '● Disconnected'}
+              </span>
+            </div>
+            
+            {consumerStatus ? (
+              <div className="consumer-status-details">
+                <div className="status-row">
+                  <label>Transaction ID:</label>
+                  <span>{consumerStatus.transaction_id.substring(0, 12)}...</span>
+                </div>
+                {consumerStatus.amount && (
+                  <div className="status-row">
+                    <label>Amount:</label>
+                    <span>${consumerStatus.amount.toFixed(2)}</span>
+                  </div>
+                )}
+                {consumerStatus.merchant && (
+                  <div className="status-row">
+                    <label>Merchant:</label>
+                    <span>{consumerStatus.merchant}</span>
+                  </div>
+                )}
+                <div className="status-row">
+                  <label>Fraud Score:</label>
+                  <div
+                    style={{
+                      padding: '4px 8px',
+                      backgroundColor: getFraudScoreColor(consumerStatus.fraud_score),
+                      color: 'white',
+                      borderRadius: '4px',
+                      fontWeight: 'bold',
+                    }}
+                  >
+                    {(consumerStatus.fraud_score * 100).toFixed(1)}%
+                  </div>
+                </div>
+                <div className="status-row">
+                  <label>Decision:</label>
+                  <div
+                    style={{
+                      padding: '4px 8px',
+                      backgroundColor: consumerStatus.decision === 'blocked' ? '#ef4444' : '#10b981',
+                      color: 'white',
+                      borderRadius: '4px',
+                      fontWeight: 'bold',
+                      textTransform: 'uppercase',
+                    }}
+                  >
+                    {consumerStatus.decision}
+                  </div>
+                </div>
+                <div className="status-row">
+                  <label>Processed:</label>
+                  <span>{new Date(consumerStatus.timestamp).toLocaleString()}</span>
+                </div>
+              </div>
+            ) : (
+              <div className="empty-state">
+                <p>Waiting for fraud detection results...</p>
+                <p style={{ fontSize: '12px', color: '#6b7280' }}>
+                  Submit transactions to see results
+                </p>
+              </div>
+            )}
+          </div>
+        </section>
+
         {/* Authentication Section */}
         <section className="card auth-card">
           <div className="card-header">
@@ -308,8 +475,58 @@ const App: React.FC = () => {
               <Clock size={20} />
               <h2>Transaction Results</h2>
             </div>
+            
+            {/* Pagination Controls */}
+            <div className="pagination-controls">
+              <div className="pagination-info">
+                <span>
+                  Showing {paginatedResults.length > 0 ? (currentPage - 1) * pageSize + 1 : 0}–
+                  {Math.min(currentPage * pageSize, results.length)} of {results.length} transactions
+                </span>
+              </div>
+              
+              <div className="pagination-buttons">
+                <button
+                  onClick={() => setCurrentPage(Math.max(1, currentPage - 1))}
+                  disabled={currentPage === 1}
+                  className="btn btn-pagination"
+                >
+                  <ChevronLeft size={16} /> Previous
+                </button>
+                
+                <span className="page-indicator">
+                  Page {currentPage} of {totalPages || 1}
+                </span>
+                
+                <button
+                  onClick={() => setCurrentPage(Math.min(totalPages, currentPage + 1))}
+                  disabled={currentPage === totalPages}
+                  className="btn btn-pagination"
+                >
+                  Next <ChevronRight size={16} />
+                </button>
+              </div>
+              
+              <div className="page-size-selector">
+                <label>Items per page:</label>
+                <select
+                  value={pageSize}
+                  onChange={(e) => {
+                    setPageSize(parseInt(e.target.value));
+                    setCurrentPage(1); // Reset to first page
+                  }}
+                  className="select-input"
+                >
+                  <option value={10}>10</option>
+                  <option value={25}>25</option>
+                  <option value={50}>50</option>
+                </select>
+              </div>
+            </div>
+            
+            {/* Results List */}
             <div className="results-list">
-              {results.map((result, idx) => (
+              {paginatedResults.map((result, idx) => (
                 <div key={idx} className="result-item">
                   <div className="result-content">
                     <p className="result-id">